1. Field of the Invention (Technical Field)
The present invention relates to windows for distributed aperture sensors.
2. Description of Related Art
Distributed aperture sensors comprise a collection of sensors mounted either around a vehicle or co-located in one location where an unobstructed 360 degree line-of-sight (or other field of view requiring more than one sensor aperture) can be obtained. Each aperture will ordinarily comprise a window.
The electromagnetic (EM) capabilities of different window materials and resistivities play an important role in the EM compatibility of host vehicles and the performance of on-board sensors. In the mid-wave infrared, there is a trade between high and low bulk resistivity silicon (Si) windows. The former provides high transmission for optimal sensor performance, while the latter provides increased conductance for low radar cross sections (RCS). In the past, a relatively expensive compromise was utilized to provide the benefits of both types of materials by overlaying the bulk Si substrate material with a low resistivity epitaxial layer. These materials represented a major cost and schedule impact due to the number of steps and amount of material processing, the high degree of precision and the tolerances that had to be maintained, and the requirement for special handling and tools necessary for producing the finished product.
Recent advances in materials processing, however, have made available materials that can be better tuned for bulk resistivity. These bulk materials are readily available and can be readily provided at a substantially lower cost.
The present invention recognized that these bulk materials exhibit performance properties that make them candidates for a lower cost replacement for the epitaxial layer equipped window substrates for distributed aperture sensor windows. Results indicate that a simple, scaleable, readily available, cost and performance effective alternative exists to the traditional expensive, complex, multi-layer applications currently implemented.